User`s guide

4 Connecting to Hardware
Star ting and Stopping a Video Input Object
When you create a video input object, y ou establish a connection between
MATLAB and an image acquisition device. However, before you can acquire
data from the device, you must start the object, using the
start function.
start(vid);
When you start an object, you reserve the device for your exclusive use and
lock the configuration. Thus, certain properties become read only while
running.
An image acquisition object stops running when any of the following
conditions is met:
• The requested number of frames is a cquired. This occurs when
FramesAcquired = Fram esPerTrigger * (Trigger Repeat + 1)
where FramesAcquired, Fram esPe rTrigger,andTriggerRepeat are
properties of the video input object. For information about thes e properties,
see Chapter 5, “Acquiring Image Data”.
• A run-time error occurs.
• The object’s
Timeout v alue is reached.
• You issue the
stop function.
When an object is started, the toolbox sets the object’s
Running property to
'on'. When an object is not running, the toolbox sets the object’s Running
property to 'off'; this state is called stopped.
4-24